1. Field of the Invention
This invention relates to a TiO.sub.2 pigment with a porous coating of alumina and a dense coating of alumina, such dense coating being formed in the presence of soluble molybdate. It is suitable for applications requiring a combination of high gloss and good durability. This invention also relates to a process for preparing such coated TiO.sub.2 pigment.
Treatment of TiO.sub.2 pigment with hydrous oxides, especially silica and alumina, is known to provide good dispersion and durability, or resistance to chalking, in paints. TiO.sub.2 pigments with a silica coating have good durability but tend to be inadequate in applications requiring high gloss, for example, automobiles and household appliances.
This invention provides for a TiO.sub.2 pigment coated in such a way as to combine good durability with high gloss.
2. Description of the Prior Art
U.S. Pat. No. 4,052,223 discloses a process for producing a durable TiO.sub.2 pigment which is coated with a phosphate, a silicate, and hydrous oxides of zirconium and aluminum, in carefully controlled amounts and order of deposition.
U.S. Pat. No. 4,405,376 discloses a TiO.sub.2 pigment with good durability and dispersibility, having an inner coating of hydrous oxides of tin and zirconium, and an outer coating of hydrous alumina; and a process for producing the pigment.